THE MECHANICS OF SKI-BINDINGS
The shoe--The original bindings--The modern bindings--The
foot--The hinge in the foot--Different functions of the
toe-strap and heel-band--The parts of the binding--Faulty
fasteners--Sketches of faulty and correct leverage--A schematic
binding--_Critique_ of bindings in use--Suggestions--Cheeks and
plates--A whole blade--Cause of strained feet--Steel wire in
bindings.
In choosing a suitable binding for the high-level routes in the Alps--as
in thinking out or devising such a binding--the runner’s commodity is the
main consideration. There is human anatomy. There are the possibilities
of leather, metal, and wire. And footgear, and ski, and binding have to
work together.
Runners who run for sport alone have a preference for the boots known
in the trade under the name of laupar boots. They are thick-soled,
flat-heeled, box-shaped above the toes. The Lotus boots, made on an
American shape, are a good type also. But are they good Alpine boots?
Runners in the Alps for whom ski are a means to an end, as well as an
object in itself, generally wear an ordinary mountaineering boot of a
large size, carefully nailed on heel and sole. This for two reasons:--
First, there is frequently some distance to be travelled over, in order
to get across the rough, broken, or wooded ground before reaching the
high snow-fields.
Second, it is practically impossible to dispense with nails in one’s
boots when crossing, above the snow-line, rocks and icy patches. On these
ski are useless. They have to be carried for awhile or left behind, till
called for. The runner is then thrown upon his boots and climbing-irons.
Should his boots be laupars, the climbing-irons have to be fitted on to
the bare soles. This is an inconvenient process, partly because the bands
are liable to freeze, partly because it may take more time to don and
doff the irons than the emergency will be kind enough to allow.
Those who speak of injury done to ski-blades by boot-nails carry too
far their sympathy for an excellent servant. In point of fact, a
symmetrically and regularly nailed boot makes upon the ski-blade and
plate a harmless impression. The lodgement of each nail-head is clean. It
even affords an additional support when turning, or breaking, or swinging.
The characteristics of a good running boot are, as one sees, few and
definite.
With ski bindings, or fastenings, the matter is altogether different.
The popularity of ski-running burst forth so suddenly upon the sporting
world that the invention of new bindings--of which there is no end--soon
proceeded even beyond the boundaries of common sense and reason.
The original Scandinavian and Lap bindings, with bent twigs, twisted
cane, or long thong, were quite sufficient for their purpose and in their
place.
Of the new bindings a large number are of a commercial character only.
Others, brought out on the score of mechanical perfection, come forward
with purely academical credentials.
The early Scandinavian or Norse fastenings had a distinct quality.
They were not invented, but grew. They were made of one same material
throughout, showing the essential feature of a sound binding: uniformity
of texture. But the ski-blade was directly fastened to the foot, more
particularly to the toes, by the binding.
The defect of these original bindings came to light when they were put
to more athletic uses. They then proved too weak, and not sufficiently
durable, in the hands of Germans, Austrians, and Swiss, practising the
Norse sport in their own countries.
Iron and steel, in varying degrees of hardness, were pressed into
service. The uniformity of material was thus brought to an end.
To make a long story short, the Huitfeldt and Ellefsen bindings are
generally admitted to be the most useful. The former is distinguished
by a clamp for bolting down the heel-strap. The latter obtains
rigidity--which is considered indispensable--by binding the heel of the
runner to the ski-blade by means of a stiff sole.
Whatever the binding, the mechanics controlling the linking together of
limb, boot, and ski in common action, need some explaining. Even the
lay-reader may gain some benefit from a short and easy excursion in the
domain of _technique_.
The foot consists of toes, ball, and heel. The point of play is the same,
whether one walk or use ski. It lies across the ball of the foot. It
is determined by the structure and articulations of the foot, from the
extremity of the big toe to above the ankle-joint. But the line of play
does not lie _along_ the foot; it lies athwart. On this line turns or
hinges the foot, as though a rod were run through it, whether the motion
be up and down--that is, vertical; or horizontal (right and left); or
oblique (foot sideways and edgeways), as in turns, swings, &c.
There is thus an axis of rotation through the foot. This axis need no
more be horizontal than, for instance, the wheels of a motor-car when one
drives over an obstacle.
The foot should sit at ease in the binding. It must not be fretted,
chafed, galled, or pressed by the material of the binding when the work
to be done puts a long and enduring strain on the boot. To that effect,
the binding should be such that the pressure will, as it were, cancel
itself by an equal application and even distribution, whatever may be the
movements and position of the foot.
In other words, the heel-strap must have its point of attachment on the
axis of rotation across the foot, the point on which it revolves to
describe some portion of a circle in the vertical direction.
But this attachment must be mobile throughout in the horizontal plane.
It should not be fixed on to the side of the ski-blade, or upon the ski
in front of the foot, or anywhere else. One should bear in mind that, in
mechanics, a heel-strap adhering to the ski at the centre of revolution
acts like a rigid arm. The balance of the body is upset by sudden shocks
which may react injuriously upon the foot, whenever there is a rigid
connection brought into play, if only for one instant.
It is the business of the toe-strap to establish a connection (a close
and immobile connection) between the foot and the ski, which it is the
foot’s function to propel. To the contrary, to perform its office,
the heel-strap requires no fixed points of vertical support. In a
mechanically perfect binding, the foot of the runner would be free to
revolve, as on a pivot, in the horizontal plane, spending thus forces of
lateral origin, while the ski continued upon its course. As it is, a good
runner surmounts disturbing, incidental forces (the ordinary cause of
accidents arising from ski-structure) by passing them up along his body
and neutralising their effect by shooting himself upwards, as if to fly.
When twigs of twisted cane were used they broke away under the strain.
The long leather thong was stronger, but it froze, or imbibed water with
too much alacrity.
A ski-binding is essentially composed of four parts:--
First: A ring, or toe-strap, in which to adjust the point of the foot,
and which is the _fulcrum_.
Second: A heel-band, which, passing round the foot, presses its fore-part
against the _fulcrum_, in the ring, or toe-strap.
Third: A fastener, either clamp, bolt, buckle with eye and prong, sole
of appropriate length, lever, &c., wherewith to regulate and adjust the
pressure of the heel-band upon the _fulcrum_.
Fourth: Side-supports, or cheeks, for the ball of the foot, generally
placed on each side of the _fulcrum_.
It is under number three (clamps, buckles, and levers) that all
fastenings are at fault. They would have to be self-adjusting, so far
as quick adaptation to changing weather conditions and sudden running
strains is necessary. But such cannot be automatically obtained yet. The
best fasteners are approximate in their action. The worst are clumsy
mechanical contrivances. Most, good or bad, link the heel-band with the
ski blade. Some fasteners are placed on one or both cheeks.
[Illustration: FAULTY LEVERAGE.]
We have already made it plain: the heel-band, when stretched out round
the foot, should be free to revolve in the same plane as the flat of the
ski, as set forth in the following sketches:--
Here lateral impulses or checks are transmitted through the point of
attachment of the heel-band.
[Illustration: CORRECT LEVERAGE.
A. Oblique View.
B. Front View.]
Here none but the pressure exerted by means of the heel-band fastener
upon the _fulcrum_ (toe-straps and cheeks) controls the ski.
If the reader will kindly remember what we said about the axis of
rotation lying across the ball of the foot, he will now understand that
the heel-band has to describe “some portion of a circle” on the apex A,
as follows:--
[Illustration: CORRECT LEVERAGE.
Side View.]
each time the foot moves up and down in the vertical line.
Consequently the principles of a schematic binding work out in this way:--
First: That the heel-band be free to move in a horizontal plane, and be
made to run through the fastening lever instead of being itself attached
to the ski by an extremity.
Second: That the heel-band run loosely through a loop or sleeve placed on
the apex of the foot axis on each side of the ball of the foot. The band
will hinge on the loop, else it would slacken and tighten as the foot
rises and falls.
Third: That the heel-band be of the nature of a continuous rope, or
closed circuit, passing through the handle of the lever which, when
opened or shut, releases the foot, or presses it down into the toe-strap.
Fourth: That the heel-band hang upon each apex of the rotatory axis
instead of being tied there.
There are many reasons for accepting the above remarks. For instance, the
point of rotation works out too high in many manufactured bindings. The
heel-strap then cannot adhere as it should to the boot. Its radius and
that of the heel do not coincide. In the case of a well-known Norwegian
binding, the strap, on the contrary, starts from a point of attachment
which, on each side of the ski, is placed lower than the toe-line. Thus
the heel-strap is wrongly centred again. The boot undergoes irregular
pressure, a cause of additional fatigue and a waste of mechanical power.
Most makers have been led into this fault by the bulk and thickness of
the material ordinarily employed--namely leather. Leather does very well
for circling the heel, a flat band being there the proper thing to be
used, but it is less useful to the front, where tension is called for.
The fore part of the heel-band might perhaps be replaced by a rope of
fine strands of wire, with a breaking strain equal to, say, six hundred
pounds, by far exceeding the strength of the stoutest ski-thong. At the
point of rotation, the strap, in which is placed the heel, would meet
the wire. Thus the connecting-point between the heel-strap and its wire
extremities to the front would coincide with the pivots on which the heel
revolves in the axis of the foot.
Under those conditions, when lifting from the ski the heel of the boot,
the tension of the heel-band remains uniform in every position.
This part of the binding apparatus may be practically autonomous. Free
from any direct connection with the wood, it ceases to be a medium
through which shocks may disturb the balance of the body. The foot then
is free to exercise unhindered its own balancing power and to obey its
spontaneous “statics.”
When cheeks are used, they generally consist of two steel plates, with
turned-up sides or ears, and frequently provided with holes at suitable
distances. Hammered into shape, the plates usually overlap each other on
the centre line of the ski. Sometimes a pin driven through any two holes
in the superposed plates (by means of a spring, to which it is attached)
maintains the plates at such a distance from each other as may fit the
boot of the runner.
Plates need not be inserted through the wood of the ski, as is the case
with most bindings with cheeks, but they may be laid on the flat of the
blade, quite on a level with the rotatory axis of the foot. A steel
spring may then be adjusted along the middle line of the foot-rest. It
may be raised with the greatest ease, bringing the pin with it.
To the usual practice of boring a hole through the wood of the ski should
be preferred an arrangement such as we have just described, preserving
for the runner that on which he most justly may pride himself: a whole
and uninjured ski-blade.
The writer has always used in the High Alps a binding fulfilling the
conditions here laid down. He found his binding both safe and strong.
Elasticity and uniformity of pressure are so well secured by the
severance of the heel-band from the body of the ski, that a fall forward
is not accompanied by an awkward strain, such strain being almost always
brought about by the reaction of the weight of the ski upon the muscles
or bones of the foot. It is now generally recognised that strains and
breaks are not caused by the firmness of a binding, but by an unequal and
jolting application of pressure to the bones and muscular tissues.
A binding, the whole of which may be detached from the ski-blade by
taking out a pin and removing a lever, is handy to travel with, as
instruments to fit on a new binding instead of an old or broken one, are
inconvenient adjuncts.
The weak points in steel rope bindings are:--
1. That the rivet connecting wire and leather may give way. The splicing
should be most carefully seen to.
2. The metal cheeks may turn out to be brittle, if too hard or too thin,
as in any other binding with cheeks.
3. The soft steel wire being made of strands, the very condition of its
pliancy, this also means that the strands may be too soft, or too hard,
or that they may be broken or unwound by coming into contact with hard
edges. To obviate this risk, an oiled leather sleeve through which the
wires might run, would protect them against friction and provide them
with a lubricant.
The lubricant should be applied also on the bends of the wire.
The leather sleeves are placed outside each cheek by means of a rivet
with the loop upwards and free. This provides a non-rigid “focus” of soft
material, through which the fine wires, though tense, run loosely. The
section of the wire thus enclosed lies at a varying angle with the foot
as it rises and falls, and adjusts itself to this in its every position.
The lever by means of which the tightening of the wire heel-strap is
managed, is best placed across the ski-blade in front of the foot. The
wire runs freely through this lever to which, as mentioned before, it
should not be attached. Thus, in case of a wrench, or should the runner
fall, the whole of the wired heel-band may yield to the foot and shift
it just a little to one side or the other, instead of jerking it, as is
otherwise common, either against or out of the binding.
Be this as it may, and taking things at their best, the modern
ski-runner’s desideratum--a binding of uniform material, adaptable and
elastic throughout--has yet to be met.
An occasionally rather heated warfare was, a few years ago, waged in
words, all about ski-bindings. The shape, length, breadth, and grooving
of the ski-blades were also drawn into the field of controversy. Such
debates are a positive relish for enthusiasts and fanatics. But, though
angry words break no bones, violent talk is apt to be vapid and, save for
the sake of exercise in vituperative wit, can serve no useful purpose.
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